Hitherto, there have been provided web services, such as SNS (Social Networking Service), allowing individual users to disclose information on the Internet. Such web services generally do not restrict another user from disclosing information related to a certain user. Posted messages or images to be disclosed sometimes contain private information of a user other than the person who posted the messages or images.
In view of such circumstances, there are provided services for outputting an alert when a preset keyword is disclosed (see, for example, NPL 1). Also, there have been proposed techniques, such as a technique of warning a user of a privacy violation (see, for example, PTL 1), a technique of analyzing posted data and calculating urgency (see, for example, PTL 2), a technique of automatically updating privacy settings (see, for example, PTL 3), and a technique of automatically creating a profile (see, for example, PTL 4).